The Atlantic salmon is an iconic species in the north Atlantic Ocean and historically supported large fisheries throughout its range. There are three distinct populations of Atlantic salmon – North American, European, and Baltic. Like all salmons, this species is noted for undergoing long migrations and significant physiological changes during a transition in habitat from freshwater rivers, to coastal seas, and back to freshwater rivers.
Adult Atlantic salmon live in coastal seas and feed on pelagic invertebrates and some fishes. During the oceanic portion of their life cycle, these fish are primarily concerned with growing and storing energy that they will require for successful reproduction. This period typically lasts for 2-3 years. Once they reach reproductive size, they begin a long migration to their preferred spawning ground, fair inland, in freshwater rivers. Interestingly, though the three populations mix at sea, they divide into their respective groups to reproduce. In fact, each individual Atlantic salmon returns to spawn in the river where it hatched, so rivers around the north Atlantic are home to distinct subpopulations of this salmon. Thousands of individuals migrate to and reach the spawning grounds at the same time. Once they arrive, females dig nests in light gravel and lay their eggs on the river bottom. Males fertilize the eggs externally, and then the females bury the nests. Unlike the pacific salmons (such as the chinook salmon), Atlantic salmon do not die after reproducing just once. They can repeat this cycle several times. After they hatch, baby Atlantic salmon spend approximately 2-3 years living in different riverine habitats as they slowly make their way to the ocean, where they stay until they reach maturity and begin the cycle again. Though this lifecycle is typical of the species, it is not required for survival. Some subpopulations are landlocked and replace the oceanic portion of their lifecycle with large, inland lakes.
Atlantic salmon are important oceanic prey for several species. This salmon was historically also an important fishery species, and Atlantic salmon fisheries have been regulated for at least 800 years in Europe. In the ocean, large boats historically targeted this species in very large numbers. While they migrate toward their spawning grounds, Atlantic salmon are targeted by fishers using traps and other semi-permanent structures installed in rivers. Unfortunately, overfishing, climate change, and competition from nonnative species all threaten Atlantic salmon, and several subpopulations are critically endangered (very highly vulnerable to extinction) or even extinct. Because individuals return to spawn in the river where they hatched, climate change is one of the most significant future threats to this species. As rivers in the southern part of their range become too warm for eggs to survive, subpopulations that spawn in those rivers will almost certainly go extinct.
Atlantic salmon are one of the most aquacultured marine fishes and are farmed in many places around the world, including outside of their native range. Now, essentially all of the Atlantic salmon sold in the seafood industry is from farms rather than from wild populations. Aquaculture of this magnitude presents its own problems, however, and escaped fish may threaten natural populations in the north Atlantic or may lead to establishment of invasive populations in other parts of the world where it is farmed.